http://starwars.wikia.com/wiki/Calendar would be a good place to start.
The year in game depends on what Chapter you are in. Prologue+Ch 1 is 3643 BBY or 10 ATC. Chapter 2 is a year later at 3642 BBY, 11 ATC. And Chapter 3 is yet another year at 3641 BBY, 12 ATC.
That seems to be results of research I've done for my character backgrounds.